| Abstrakt: |
The limited availability of analog-to-digital converters with high enough speed and dynamic range makes conventional heterodyne receivers still a reasonable solution for millimeter wave work when a wide frequency tuning range is desired. These basically well-known arrangements from the microwave bands may show surprising phenomena if the features of individual millimeter building blocks are not carefully analyzed. LNA gain below the frequency range of interest can be 10-20 dB more than expected which could severely impair the system noise performance after downconversion. Local oscillator tuning sensitivity above 1000 MHz/V, partly based on almost mandatory multiplication, together with very large tuning speed easily cause stability problems. Particularly active multipliers have often less than 20 dB rejection of fundamental frequency and unwanted harmonics output, which together with mixer LO/IF feed through can completely desensitize the front-end. An improperly matched mixer IF port may confuse even an experienced designer by phantom responses. Finally, modern logarithmic detectors chips can unexpectedly waste more than 10 dB of receiver sensitivity. [ABSTRACT FROM AUTHOR] |
